The present invention relates generally to fuel injection pumps of the type having a rotary charge pump with one or more reciprocating pumping plungers for sequentially supplying measured charges of fuel under high pressure to an associated internal combustion engine for fuel injection and relates more particularly to a new and improved spill control mechanism for spill control of the high pressure fuel charges.
In a fuel injection pump of the type described, it may be desirable to control the size and/or timing of each high pressure fuel charge by a spill control system providing spill control of the beginning and/or end of the high pressure fuel injection event. For example, U.S. Pat. No. 4,376,432 of Charles W. Davis, dated Mar. 15, 1983, discloses a spill control system providing spill control of the end of the fuel injection event.
In U.S. Pat. No. 4,552,117 and copending application Ser. No. 779,201, several embodiments of a spill control mechanism are disclosed which employ one or more rotating fuel control valves for spill control of the high pressure fuel charges. Each rotating fuel control valve is mounted on the charge pump rotor and connected to the charge pump for spill control of the high pressure fuel charges. The high pressure fuel charges are precisely controlled with a high degree of repeatability and reliability over a long service free life.
The many advantages available from the invention disclosed in said copending application, include the capability to adjust the size of the injected fuel charge in a precise and simple matter and to vary the fuel injection timing in accordance with a change in the engine load and/or engine speed. The spill timing can be adjusted at the beginning and/or end of the fuel injection event by a variety of mechanical electrical, hydraulic and/or vaccum operated means driven by the fuel injection pump or the associated engine.
The present invention is directed to an improvement over the injection pump and spill control mechanisms described in said copending application, based on simplification of the structural and functional relationships between the spill control mechanism and the rotor and drive shaft with which it is associated. This simplification has, as its primary objective, the reduction of the dead volume and two-way traffic experienced by the fuel during the sequence of filling the pumping chamber, pressurizing and discharging the fuel, spill controlling the injection event, and refilling the pumping chamber.
Another object of the invention related to simplifying the spill control mechanism associated with the rotor, is to reduce the size and strength requirements for the rotor by minimizing the components required to be mounted thereon, and by isolating the rotor from the high stresses of the mechanism used to actuate the pumping chamber in the rotor.
A third object related to simplification of the spill control mechanism, is to eliminate the need for accumulators or similar components for the desired spill control, and to substitute a simple spill pressure regulating valve.
These and other objects are accomplished by mounting the rotating spill control valve transversely in the rotor, adjacent the pumping chamber. In the preferred embodiment of the invention, the spill control valve is centered on the longitudinal axis of the rotor and connected to the center of the pumping chamber by a short pump passage or bore. Pressurized fuel from the pumping chamber is forced through the pump passage and a transverse bore in the center of the spill valve, into an outlet passage for delivery to the outlet nozzle. The forces on the valve are balanced during this injection event. Inlet fuel enters the valve bore and passes through the spill valve through another transverse bore, which is fluidly connected to the pump passage. Thus, the dead volume and two-way traffic are experienced only in the pump passage. This passage can be made significantly shorter than the analogous passage or bore known in the art, because the center of the spill valve bore to which it is connected can be located substantially adjacent to the center of the charge pump, without encumbrance by the pump plungers or charge pump actuating components.
Mounting the spill control valve transversely within the rotor permits a further advantageous feature of the preferred embodiment, a headless rotor, i.e., the rollers and shoes typically used to actuate the pumping plungers can be mounted in the drive shaft rather than in the rotor. As compared with typical rotors, the preferred headless rotors is torque-free and thus can be smaller and constructed from a less costly material.
The transversely mounted spill control valve and associated simplification of the fill and injection passageways, permits yet another advantageous feature, a simple spill pressure regulating valve. A spill control passageway extends from the valve bore to the surface of the rotor that faces a corotating surface of, for example, the drive shaft. A simple check valve in the passageway is biased towards the valve bore by spring means mounted between the drive shaft and the rotor, to provide pressure regulation of the spill control passageway. The geometry of the rotating valve member within the valve bore provides a land surface trailing edge that interacts with the pump passage and the spill control passage, to accomplish end of injection spill control.
The adjustment of fuel injection timing and quantity are accomplished by means of a cam ring and associated adjusting ear, and by adjustment of the angular relationship between the rotor and rotor valve member. The timing adjustment is preferably accomplished by a dual piston arrangement acting as a force couple on opposite sides of the cam ring. The desired effects of such adjustment are, however, accomplished only by the interaction of end-of-cycle injection control with the control of the shape of the cam rise during the injection event.